1. Field of the Invention
The disclosure generally relates to method and apparatus for simultaneous lateral and vertical patterning of molecular organic thin films via microcontact patterning. The disclosed process can be applied to fabrication of organic light emitting device arrays and has been found particularly advantageous over the conventional techniques in that large arrays can be formed without cost constraints of the conventional techniques.
2. Description of Related Art
Organic light emitting devices (OLEDs) are thin, brightly emissive and efficient diodes which have been gaining traction in display technology. OLEDs have fast switching speeds which make them ideal for flat panel display. OLEDs do not require backlighting which makes them capable of producing video displays with a fraction of the thickness of plasma or LCD displays.
A challenge in fabricating OLEDs is patterning micron-sized features of molecular organic thin films over large areas. OLEDs are typically patterned by shadow masking. In shadow masking a rigid stencil shadow mask is placed between the source material and the substrate to pattern the deposited thin film. This technique is limited in resolution due to lateral diffusion from the spacing between the shadow mask and the substrate and the thickness of the shadow mask. Experience shows that it is difficult to make large area shadow masks with features smaller than 150 μm. High-resolution displays require 30-μm-sized features.
Alternative techniques for patterning molecular organic thin films include: laser induced thermal imaging (“LITI”), laser induced pattern-wise sublimation (“LIPS”), molecular jet printing (“MoJet”) and contact stamping techniques. LITI and LIPS rely on thermal transfer of organic layer and are limited in resolution due to the ability to focus the laser. MoJet uses a Micro-Electro-Mechanical System (“MEMS”) valve to pattern the organic layer and is not limited in resolution, but the valve is susceptible to clogging. Large area scalability of these techniques requires multiple lasers or MEMS valves which is both costly and labor intensive.
The contact stamping method can produce features smaller than 30 μm by applying a patterned stamp. However, conventional contact stamping requires elevated temperature and pressure which are unsuited for OLED fabrication. Heat and pressure can be detrimental to certain organic material used in the OLED as they can cause contamination or alteration of the organic component.
Accordingly, there is a need for a method and apparatus for OLED manufacturing which enables inexpensive, precise large scale manufacturing without causing OLED alteration or contamination.